Multi-layer structure with potassium ionomer

ABSTRACT

The present invention relates to a multi-layer structure constructed of two or more layers including a potassium ionomer layer (X) having a low surface resistivity and a layer (Y) comprising a polymer material having a high surface resistivity like LLDPE as a surface layer, where the static charge decay characteristics of the layer (Y) is improved. This type of two layer or three layer structure having the layer (X) as its intermediate layer or another surface layer gives good slip characteristics, abrasion resistance, and dust-free characteristics, and hence is useful for packaging materials, such as films, sheets and containers.

TECHNICAL FIELD

The present invention relates to a multi-layer structure (laminate) having at least one layer of potassium ionomer that possesses good charge decay characteristics, slip characteristics, abrasion resistance, etc. In particular, the present invention relates to a multi-layer structure that has good processability, mechanical properties, and dust-free characteristics favorable for molding materials such as for packaging uses.

BACKGROUND ART

Olefin polymers are widely utilized in the general packaging film sector. Above all, ethylene polymers are in most common uses owing to their good heat sealability. While good slip characteristics are required in the film production process and good scratch resistance is also required in terms of the performance of the film, few ethylene polymers of general uses possess both of these properties. For instance, even though polyethylene with a wide range of densities acquires sufficient slip characteristics with the addition of slip agents, they do not demonstrate satisfactory scratch resistance. Ionomers of general uses, which inherently have good scratch resistance, are insufficient for slip characteristics.

In general, moldings produced from polymer materials readily generate static electricity and often collect dust from air while they are handled in storage, transit, and end uses, which result in pollution of the surface of moldings. In the case that the molding is a bag for powders and the like, a part of the contained powders sticks to the internal surface of the bag, often defacing the package and impairing the commercial value of the merchandise. To prevent the adhesion of dust and powders, various kinds of anti-static technologies have been proposed and put into practice. Generally adopted approaches include a method to melt-blend an antistatic agent into the molding resin composition and a method to coat the moldings with an antistatic agent or an antistatic polymer. Those methods, however, are known to have some drawbacks. For instance, the former method is often accompanied by contamination of the packaged material with bleed out of the migrated antistatic agents or the problem of time-related deterioration in the antistatic effect. As for the latter method, some defects are pointed out such as poor water resistance of the coated layer, easy damage of the coated layer, increase in surface tackiness resultant from water absorption, etc.

To improve the aforesaid shortcomings of the methods of coating of antistatic agent or antistatic polymer, some attempts have been made by providing some other surface layer on top of an antistatic polymer layer for the purpose of blanketing the antistatic polymer layer. Japanese Patent No. Hei 2 (1990)-28919, for example, proposed an antistatic plastic film comprised of a plastic substrate, an ionic conductive resin layer on it and furthermore, a water-resistant plastic layer having a volume resistivity of 1×10¹³ Ω·cm or less and a thickness of 10 μm or less on the top of the film. According to this proposal, the type of usable material is limited and therefore, it is difficult to obtain a laminated film having various properties.

Japanese Laid-open Patent Application No. Sho 61(1986)-44646 disclosed an electrostatic and bleed out-free multi-layer structure which has alkali metal salt or amine salt of an ethylene-unsaturated carboxylic acid copolymer in the intermediate layer. Moreover, Japanese Laid-open Patent Application No. Hei 10(1998)-193495 proposed a dust-proof multi-layer structure, which has an intermediate layer composed of a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer and a polyhydroxy compound to improve antistatic effect in low humidity over the aforesaid technique. It disclosed comparative examples that showed antistatic properties were insufficient in those multi-layer structures described in the aforesaid techniques.

The present inventors have engaged in research efforts to obtain a material that has good heat sealability, dust-free characteristics, slip characteristics, scratch resistance, etc. to be suitable for a packaging material, and, as the result, discovered that a specific multi-layer structure gives excellent properties in all of those aspects. The present inventors furthermore discovered that a specific multi-layer structure can provide excellent dust-proof properties without added polyhydroxy compounds, as mentioned in the latter proposal, if an appropriate polymer is selected as the surface layer.

Accordingly, an object of the present invention is to provide a dust-free multi-layer structure which has good dust-free characteristics, slip characteristics, scratch resistance, etc. and is capable of avoiding electrostatic accumulation of dust, powder or the like.

DISCLOSURE OF THE INVENTION

The present invention relates to a multi-layer structure comprising at least two layers including a layer comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer or a mixture of such potassium ionomer and a thermoplastic polymer (the layer (X)), and a layer comprising a polymer material having a surface resistivity of 1×10¹⁴ Ω or more (the layer (Y)) wherein at least one surface layer has a 10% charge decay time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%.

A preferred embodiment of the present invention is a multi-layer structure comprising at least two layers including the layer (X) comprising a potassium ionomer of ethylene-unsaturated carboxylic acid polymer or a mixture of said potassium ionomer and a thermoplastic polymer wherein at least one surface layer (Y) comprises a polymer material having a surface resistivity of 1×10¹⁴ Ω or more and the layer (Y) has a 10% charge decay time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%.

It is preferable that in this preferred embodiment, the layer (X) occupies the position of the other surface layer of the above mentioned structure and the both surface layers have a 10% charge decay time of 20 sec or less at +5,000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%. Such multi-layer structure is suitable for the purpose of film, sheet for packaging, decorative, or auto exterior or interior use, blow molded container etc. Among all, a structure having a coefficient of friction of 1 or less is preferred. This type of structure is favorably used for bags and multi-layer containers.

It is also preferable that in the preferred embodiment, a multi-layer structure comprises at least three layers, wherein (a) the layer (X) occupies the position of the intermediate layer and the other surface layer (Z) comprises a polymer material having a surface resistivity of 1×10¹⁴ Ω or more, (b) the surface layer (Y) has a 10% charge decay time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%, and (c) the surface layer (Z), too, has a 10% charge decay time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity 50%. Multi-layer structures of the aforesaid type are useful for applications involving film, sheet, bags and multi-layer containers.

PREFERRED EMBODIMENTS OF THE INVENTION

The layer (X), which consists of one surface layer or an intermediate layer in the structure of the present invention, comprises a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer or a mixture of such ionomer and a thermoplastic polymer. Although a surface resistivity of the layer (X) is not limited, it ranges preferably 1×10¹² Ω or less, more preferably 1×10¹¹ Ω or less, and furthermore preferably 1×10¹⁰ Ω or less. As to the potassium ionomer of the layer (X), the ethylene-unsaturated carboxylic acid copolymer employed as its base polymer is produced by copolymerizing ethylene with an unsaturated carboxylic acid and furthermore another polar monomer that is/are optionally chosen.

As unsaturated carboxylic acid, acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, monomethyl maleate, monoethyl maleate, etc. can be exemplified here. Acrylic acid or methacrylic acid is particularly preferable. In addition, as other polar monomers which can be copolymerization components, a vinyl ester such as vinyl acetate, vinyl propionate; an unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, iso-octyl acrylate, methyl methacrylate, ethyl methacrylate, dimethyl maleate, diethyl maleate; carbon monoxide, etc. are cited. In particular, an unsaturated carboxylic acid ester is a suitable copolymerization component. The above ethylene-unsaturated carboxylic acid copolymer can be obtained by radical copolymerization of ethylene and unsaturated carboxylic acid with other optional polar monomers under high temperature and high pressure.

In cases where the ethylene-unsaturated carboxylic acid copolymer employed as the base polymer of the potassium ionomer has an excessively small acid content or the potassium ionomer has an excessively low degree of neutralization, a multi-layer structure, which has good dust-free characteristics and has the surface layer (Y) with an intended value of a 10% charge decay time at +5000V applied voltage, cannot be obtained. It is, therefore, desirable to employ one type or two or more types of potassium ionomers of ethylene-unsaturated carboxylic acid copolymer, where the unsaturated carboxylic acid content of the base ethylene-unsaturated carboxylic acid copolymer (or the average unsaturated carboxylic acid content of the base ethylene-unsaturated carboxylic acid copolymers) is 10 to 30% by weight, and preferably 10 to 25% by weight, and the degree of neutralization by potassium is 60% or more (60 to 100%), and preferably 70% or more (70 to 100%). With a view to obtaining a multi-layer structure possessing excellent dust-free characteristics in the present invention, it is desirable to employ the mixture of the potassium ionomers of two types or more of ethylene-unsaturated carboxylic acid copolymers varying from each other/one another in the average acid content. An example is mixed ionomers with 60% or more, and preferably 70% or more, neutralization by potassium ion of the ethylene-unsaturated carboxylic acid copolymers varying from each other/one another in the acid content; namely, the difference between the highest content and the lowest content, by 1% by weight or more, and preferably 2 to 20% by weight, while such two or more types of copolymers have an average acid content of 10 to 30% by weight, and preferably 10 to 20% by weight. More specifically, particularly favorable is mixed ionomers with the aforesaid degree of neutralization (60% or more) for the mixed copolymers components that has an average unsaturated carboxylic acid content of 10 to 30% by weight, and preferably 10 to 20% by weight and an average melt flow rate of 1 to 300 g/10 min, more preferably 10 to 200 g/10 min, and furthermore preferably 20 to 150 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g. This mixed ionomers preferably comprises ionomers of mixtures of an ethylene-unsaturated carboxylic acid copolymer having an unsaturated carboxylic acid content of 1 to 10% by weight, and preferably 2 to 10% by weight and a melt flow rate of 1 to 600-g/10 min and preferably 10 to 500 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g (the copolymer (A-1)) and an ethylene-unsaturated carboxylic acid copolymer having an unsaturated carboxylic acid content of 11 to 25% by weight, and preferably 13 to 23% by weight and a melt flow rate of 1 to 600 g/10 min, and preferably 10 to 500 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g (the copolymer (A-2)). It is preferable that the mixed polymer composition as the base polymer of the mixed ionomers is prepared by blending the copolymers A-1 and A-2 in the ratio of 5 to 80 parts by weight, and preferably 10 to 70 parts by weight for A-1, and 95 to 20 parts by weight, and preferably 90 to 30 parts by weight for A-2.

The ethylene-unsaturated carboxylic acid copolymer, as a base polymer of the potassium ionomer, may contain another polar monomer as has already been mentioned by, for instance, 40% by weight or less. In case that the layer (X) is employed as the surface layer, a polar monomer content of the copolymer has to be 30% by weight or less, and preferably 15% by weight or less, because the presence of an excessive amount of polar monomer in the copolymer exerts an adverse effect on slip characteristics and scratch resistance.

It is also desirable to employ a potassium ionomer which has a melt flow rate of 0.1 to 100 g/100 min, and particularly 0.2 to 50 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g in consideration of its intended processability, scratch resistance, or miscibility in case another component is blended.

For the multi-layer structure of the present invention, the aforesaid potassium ionomer is used as one of the surface layers or the intermediate layer. Such layer (X) may be a potassium ionomer by itself, but another thermoplastic polymer may be blended to the extent that the antistatic properties, slip characteristics and scratch resistance of the structure are not greatly impaired. Such thermoplastic polymer may be selected from polymer materials usable as the surface layer (Y) that are described later. It is preferable to use olefin-based polymers, especially ethylene-based polymers selected from ethylene homopolymers, copolymers produced from ethylene and an alpha-olefin having 3 or more carbon atoms, copolymers produced from ethylene and vinyl acetate or an unsaturated carboxylic acid ester, etc. It is not a requisite condition to employ virgin resin for such ethylene-based polymers. For instance, in cases where an ethylene-based polymer is used for the surface layer, reject products and scrap materials such as trimmed edges produced in the plastic molding operation may be recycled. Preferred blending ratio of thermoplastic polymer are 95% by weight or less, preferably 90% by weight or less, and particularly preferably 60% by weight or less as compared with the total amount of the potassium ionomer layer (X). In other words, it is desirable that the potassium ionomer accounts for 5% by weight or more, preferably 10% by weight or more, and particularly preferably 40% by weight or more of the potassium ionomer layer (X) as a whole.

In the potassium ionomer layer (X), polyhydroxy compounds having two or more of alcoholic hydroxyl groups can be compounded to improve antistatic properties. The specific examples include polyoxy alkylene glycols with various molecular weights such as polyethylene glycol, polypropylene glycol and polyoxy ethylene-polyoxy propylene glycol; polyhydric alcohols such as glycerin, hexanetriol, pentaerythritol, sorbitol and ethylene oxide adducts thereof, and adducts of multivalent amines and alkylene oxides.

An effective blending ratio of a polyhydroxy compound is desirously in the range that does not detract a mechanical characteristics of the layer (X), for example, 15% by weight or less, preferably 10% by weight or less, more preferably 5% by weight or less, the most preferably less than 0.1% by weight.

In the multi-layer structure of the present invention, polymer materials (excluding the same resin or resin composition as that of layer (X)) having surface resistivity of not less than 1×10¹⁴ Ω is used for one surface layer (Y). Surface resistivity of the polymer materials in the present invention is measured at 23° C. under an atmosphere of 50% relative humidity.

The polymer materials of the layer (Y) in the present invention are such materials that when they are molded singly, the moldings show not less than 1×10¹⁴ Ω of surface resistivity. As examples of such polymer materials, there can be cited olefin-based polymers such as homopolymers of ethylene or copolymers of ethylene and alpha-olefin having 3 to 12 carbon atoms such as high pressure polyethylene, middle or high density polyethylene, linear low density polyethylene, especially linear low density polyethylene having density of not more than 940kg/m³, and ultra low density polyethylene; polypropylene; poly-1-butene; poly-4-methyl-1-pentene; copolymers of ethylene and polar monomer such as ethylene-vinyl acetate copolymer; copolymers of ethylene and unsaturated carboxylic acid such as acrylic acid, methacrylic acid, monoethyl maleate and maleic anhydride; or ionomers thereof such as Na, Li, Zn, Mg or Ca ionomer; copolymers of ethylene and one or more kinds of unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, 2-ethyl hexyl acrylate, methyl methacrylate, glycidyl methacrylate and dimethyl maleate; terpolymers of ethylene, the above unsaturated carboxylic acid and unsaturated carboxylic acid ester, or ionomers thereof such as Na, Li, Zn, Mg or Ca ionomer; copolymers of ethylene, carbon monoxide and optional unsaturated carboxylic acid ester and vinyl acetate; and polyolefin-based elastomer; styrene-based polymers such as polystyrene and rubber-reinforced styrene-based resins like high impact polystyrene and ABS resin; polyesters such as polyethylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polyethylene naphthalate, polyethylene telephthalate copolymerized with cyclohaxane-dimethanol and polyester elastomer; poly carbonates; and poly methyl methacrylate, or mixtures of not less than two kinds of these. Among those polymer materials it is preferable to employ the olefin-based polymers which give good sealability, particularly ethylene homopolymer, a copolymer produced from ethylene and an alpha-olefin having 3 or more carbon atoms, such as linear low density polyethylene, a copolymer produced from ethylene and a polar monomer, etc. In particular, it is preferable to use such material as selected from zinc ionomer and ethylene-based polymers produced using metallocene catalyst, since the multi-layer structure using these materials provide excellent heat sealability and the surface layer (Y) capable of giving good dust-free characteristics even though a polyhydroxy compound is not added in the layer (X).

The zinc ionomer is produced by partially neutralizing the ethylene-unsaturated carboxylic acid copolymer with zinc ion, in which another polar monomer may optionally be copolymerized and it may have another metal ion coexisting with zinc.

Herein, as unsaturated carboxylic acid, acrylic acid, methacrylic acid, fumaric acid, maleic anhydride, monomethyl maleate, monoethyl maleate are exemplified, and particularly acrylic acid or methacrylic acid is preferable. In addition, as other polar monomers which can be copolymerization components, vinyl ester such as vinyl acetate and vinyl propionate; unsaturated carboxylic acid ester such as methyl acrylate, ethyl acrylate, isopropyl acrylate, n-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, iso-octyl acrylate, methyl methacrylate, dimethyl maleate and diethyl maleate acid; and carbon monoxide are cited. Particularly an unsaturated carboxylic acid ester is a suitable copolymerization component.

The ethylene-unsaturated carboxylic acid copolymer which is employed as the base polymer of the zinc ionomer preferably has an unsaturated carboxylic acid content of I to 25% by weight, and particularly 5 to 20% by weight, while the polar monomer which may optionally be copolymerized is to be contained by, for example, 40% by weight or less, and preferably 30% by weight or less. Preferred for the zinc ionomer is one that has a degree of neutralization of 10 to 90%, and particularly 15 to 80%. Moreover, in consideration of the intended processability and practicable physical properties, it is preferable to employ a zinc ionomer having a melt flow rate of 0.1 to 100 g/10 min, and particularly 0.2 to 50 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g.

The ethylene-based polymer manufactured in the presence of metallocene catalyst which is favorably employed as a polymer material of the surface layer (Y) is to be ethylene homopolymer or a copolymer produced by copolymerizing ethylene with an alpha-olefin having 3 or more carbon atoms, and preferably 3 to 12 carbon atoms, which is produced by polymerizing or copolymerizing ethylene in the presence of a catalyst formulated from a catalyst component comprised of a compound of a Group IVB transition metal, preferably zirconium, having at least one or more ligands of the cyclopentadienyl structure, and an organoaluminum-oxy compound catalyst component and, if necessary, various additive components.

As the alpha-olefin having not less than 3 carbon atoms in the above ethylene copolymer, propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecen and 4-methyl-1-pentene can be exemplified. Particularly copolymer of alpha-olefin having around 3 to 12 carbon atoms is preferably used.

Although there can be employed as the ethylene polymer or copolymer manufactured in the presence of metallocene catalyst those materials which have varied density values in accordance with the alpha-olefin content of the copolymer, it is generally desirable to employ an ethylene copolymer having a density of 870 to 970 kg/m³, particularly 890 to 950 kg/m³, and more particularly 900 to 940 kg/cm. In the light of the intended processability and practical physical properties, it is preferable to employ one that has a melt flow rate of 0.1 to 100 g/10 min, particularly 0.2 to 50 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g.

The multi-layer structure of the present invention is constructed of at least two layers comprising the potassium ionomer layer (X) and the layer (Y) which is a polymer material having a surface resistivity of 1×10¹⁴ Ω or more. This structure may be constructed of two layers with the layer (X) and the layer (Y) consisting of the respective surface layers. In this case, however, another thermoplastic polymer layer or an adhesive layer may be provided between the two surface layers. The multi-layer structure of the present invention may be constructed of three or more layers with the layer (Y) consisting of one surface layer and the layer (X) consisting of an intermediate layer. In this case, the surface layer (Z) other than the layer (Y) can be a polymer material (excluding the same resin or resin composition as that of layer (X)) having a surface resistivity of 1×10¹⁴ Ω or more, which is comparable with the layer (Y). Even in this case, another thermoplastic polymer or an adhesive layer may be provided between the layer (Y) and the layer (X) or between the layer (X) and the layer (Z). The polymer materials exemplified as for the layer (Y) can be cited as examples of the thermoplastic polymer layer. This layer may also be a layer of recycled resin produced from retrieved reject products, trimmed edges, etc. which are generated in the multi-layer structure production. Such materials for the recycled resin layer are expected to contribute the enhancement of the interlayer adhesion, because they are basically the same as the polymer material for either surface layer, for the intermediate layer or a mixture of the two, and hence enjoy good miscibility with at least one of the surface layers and the intermediate layer.

What is usable as the adhesive layer that will serve the aforesaid purpose is any type as far as it improves the interlayer bond strength. It may be selected from those thermoplastic polymers already exemplified as the raw materials for the surface layer, or may be hot melt-type adhesives or coating-type adhesives. It is preferable from the industrial standpoint to use an adhesive, applicable to the extrusion coating process, which is selected from thermoplastics or formulations including a thermoplastic polymer blended with tackifier.

A preferred embodiment of the present invention is a three-layer structure comprised of the layer (X), the intermediate layer, and the layer (Y), wherein (a) the first surface layer (X) is a layer comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer, (b) the intermediate layer comprises either a linear low density polyethylene layer or a layer of a mixture made of 100 parts by weight of linear low density polyethylene and 100 parts by weight or less, preferably 50 part by weight or less of a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer, and (c) the other surface layer (Y) comprises a linear low density polyethylene layer. The linear low density polyethylene has a density of typically 940 kg/m³ or less. An ethylene-based polymer produced particularly by metallocene catalyst is preferred as a polymer material for the intermediate layer and the other surface layer. The thickness ratio of the aforesaid layers are preferably 10 to 90 for the first surface layer (X), 0 to 60 for the intermediate layer and 10 to 90 for the other surface layer (Y).

Another preferred embodiment of the present invention is a three-layer structure comprised of the outer layer (X), the intermediate layer, and the inner layer (Y), wherein the outer layer (X) is a layer comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer (non-foamed layer or foamed layer); the intermediate-layer is a layer comprising ethylene-unsaturated ester copolymer layer such as ethylene-vinyl acetate copolymer; and the inner layer (Y) is a layer comprising ethylene homopolymer such as low density polyethylene, medium density polyethylene, high density polyethylene, metallocene-type ethylene polymer or copolymer of ethylene and an alpha-olefin, etc. Multi-layer bottles (containers) produced by the blow molding process from this multi-layer structure demonstrate not only good dust-free characteristics, slip characteristics, and scratch resistance, but also low surface reflection gloss and hazy silk fabric-like appearance, which imparts good visual qualities to the resultant bottles.

Still another preferred embodiment of the present invention is a three-layer structure comprising the outer layer (Y), the intermediate layer (X), and the inner layer (Z) or of the outer layer (Z), the intermediate layer (X), and the inner layer (Y), wherein the outer layer (Y) and-the inner layer (Z) (or the outer layer (Z) and the inner layer (Y)) comprise polyethylene such as low density polyethylene, medium density polyethylene, high density polyethylene, etc. or an ethylene-unsaturated ester copolymer such as ethylene-vinyl acetate copolymer, and the intermediate layer (X) is a layer comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer. Multi-layer blow-molded bottles (containers) produced by the blow molding process from this multi-layer structure demonstrate good dust-free characteristics, slip characteristics, scratch resistance, etc.

The multi-layer structure of the present invention can be manufactured by the extrusion coating process, the co-extrusion process or the blow molding process. While overall layer thickness of the multi-layer structure may be optionally settled, it is preferable that the thickness is in the range of 10 to 3,000 μm, particularly 20 to 1,000 μm. In the structure of the present invention, at least one of the surface layers has a 10% charge decay time (time to reach +500V) at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50% of 20 sec or less, and preferably 10 sec or less, and more preferably 1 sec or less. In the case where the layer (X) and the layer (Y) constitute the respective surface layers, it is permissible that the layer (X) alone has said charge decay characteristic and the charge decay time of the layer (Y) exceeds 20 sec. Even in this case, however, it is preferable that the layer (Y), too, has a charge decay time of 20 sec or less, preferably 10 sec or less, and more preferably 1 sec or less. In order to achieve said values, it is preferable to set the thickness of the potassium ionomer layer (X) at 5 μm or more, preferably 10 μm or more, and the thickness of the surface layer (Y) or the combined layer, in case a recycled resin layer or an adhesive layer is incorporated into the surface layer (Y), is set at 500 μm or less, and particularly 300 μm or less. In cases-where the layer (X) is the intermediate layer and the layer (Z) is another surface layer, it is permissible that the charge decay time of the layer (Z) exceeds 20 sec as far as the decay time of the layer (Y) is 20 sec or less. Nevertheless, it is preferable that the charge decay time of the layer (Z), too, is 20 sec or less, preferably 10 sec or less, and more preferably 1 sec or less. In order to achieve said values, it is preferable that the thickness of the surface layer (Z) or the combined thickness of the surface layer (Z) and a recycled resin layer or an adhesive layer, if the latter is incorporated, is at 500 μm or less, and particularly 300 μm or less. It is preferable in the light of practical capabilities that the thickness ratio of the total thickness of the other layers to the thickness of the potassium ionomer layer is within the range of 0.1 to 100, particularly 0.5 to 50.

Various additives can be blended as required with each layer of the multi-layer structure of the present invention. As examples of such additives, antioxidants, light stabilizers, ultraviolet absorption agents, pigments, dyestuffs, lubricants, anti-blocking agents, inorganic fillers, foaming agents and foaming promoters can be cited. Especially for a multi-layer bottle whose outer layer is layer (X), the multi-layer bottle in which a foaming agent is blended with the layer (X) and foamed became a bottle having superior visual quality with a silky appearance. Such a multi-layer bottle can be obtained by foaming in blow molding, after blending around 0.1 to 10 parts by weight of organic or inorganic chemical foaming agent such as azodicarbonamide, dinitrosopentamethylenediamine, sulfonylhydrazide, sodium bicarbonate or ammonium bicarbonate per 100 parts by weight of the above potassium ionomer.

EXAMPLES

Further concrete explanation of the present invention is given below with examples, but the present invention is not limited to these examples. In addition, the materials used and performance evaluation methods of the multi-layer structure obtained in the following examples and comparative examples are shown below.

1. Materials

[Polymer Materials]

Polymer materials described in Table 1 were used.

[Potassium Ionomer]

Potassium ionomers described in Table 3, in which their raw materials are base polymers of Table 2, were used. TABLE 1 MFR* Density Surface Abb. Polymer Material Maker Brand Name g/10 min kg/m³ Resistivity Ω Note MPE-1 Metallocene LLDPE MCI Evolue SP1540 4.0 915 10¹⁴< MPE-2 Metallocene LLDPE MCI Evolue SP2040 4.0 920 10¹⁴< PE-1 LDPE MCI Mirason M401 1.6 923 6 × 10¹⁵ PE-2 HDPE MCI Hi-zex 6200B 0.36 956 6 × 10¹⁵ PE-3 LDPE MCI Mirason 16 3.7 923 6 × 10¹⁵ EVA-1 Ethylene-vinyl MDP Evaflex P1905 2.5 940 2 × 10¹⁵ VA Content Acetate Copolymer 19 wt % EVA-2 Ethylene-Vinyl MDP Evaflex P1403 1.3 930 6 × 10¹⁵ VA Content Acetate Copolymer 14 wt % EVA-3 Ethylene-Vinyl MDP Evaflex EV5274 0.8 940 2 × 10¹⁵ VA Content Acetate Copolymer 17 wt % EVA-4 Ethylene-Vinyl MDP Evaflex EV250 15 950 9 × 10¹³ VA Content Acetate Copolymer 28 wt % HM-1 Ethylene-Methacrylic MDP Himilan 1554 1.0 940 2 × 10¹⁷ Zinc Salt Acid Copolymer Ionomer HM-2 Ethylene-Methacrylic MDP Himilan 1706 0.7 970 2 × 10¹⁷ Zinc Salt Acid Copolymer Ionomer LLDPE: Linear Low Density Polyethylene, LDPE: Low Density Polyethylene HDPE: High Density Polyethylene, VA: Vinyl Acetate MCI: MITSUI CHEMICALS, INC. MDP: DU PONT-MITSUI POLYCHEMICALS CO., LTD. *Melt Flow Rate under the Load of 2160 g at 190° C.

TABLE 2 Methacrylic Acid Isobutyl Acrylate MFR* Abb. Base Polymer Content wt % Content wt % g/10 min EMAA-1 Ethylene-Metharylic Acid 15 0 60 Copolymer EMAA-2 Ethylene-Metharylic Acid 10 0 100 EMAA-3 Ethylene-Metharylic Acid 17.5 0 60 Copolymer Ethylene-Metharylic Acid- 5 10 33 EMAAIBA Isobutyl Acrylate Copolymer *: Melt Flow Rate under the Load of 2160 g at 190° C.

TABLE 3 Properties of Base Polymer Properties of K-Ionomer Average Neutrali- Added Composition Acid Con- Av. MFR* zation MFR* Polyhydroxy Abb. (weight) tent wt % g/10 min Degrees % g/10 min Cpd. Wt % KIO-1 Blend of EMAA-1(50) 12.5 78 92 5.0 PEG600 and EMAA-2(50) 10 KIO-2 Blend of EMAA-3(50) 11.3 45 80 0.6 0 and EMAAIBA(50) KIO-3 Blend of EMAA-1(50) 12.5 78 92 0.2 0 and EMAA-2(50) KIO-4 Blend of EMAA-1(50) 12.5 78 80 5.5 Glycerin and EMAA-2(50) 9 KIO-5 Blend of EMAA-3(50) 11.3 45 80 0.6 Glycerin and EMAAIBA(50) 0.5 PEG600: Polyethylene Glycol (MW:600) *Melt Flow Rate under the Load of 2160 g at 190° C. 2. Physical Property Test Methods (1) Antistatic Performance (1-1) Decay Time

After a piece of the sample film was kept at 23° C. and 50% relative humidity for 24 hours, time from +5000V of applied voltage to +500V as 10% charge decay time and time from +5000V of applied voltage to +2500V as 50% charge decay time of the sample film were measured using a Static Decay Meter Model 4060 of ETS Inc.

(1-2) Ash Attachment Test Method

Immediately after a piece of the sample film was kept at 23° C. and 50% relative humidity for 24 hours, the sample film was rubbed 10 times with a sheet of cotton cloth, ash for one cigarette was put on it and then the sample film was reversed. The ash adhesion was determined with remaining status of ash.

⊚: Ash is not remaining at all

◯: Ash is slightly remaining

Δ: Ash is sparsely remaining

×: Ash is almost remaining on the entire surface

(1-3) The Electric Potential Measurement

A multi-layer container was kept at 40° C. and 80% relative humidity for 24 hours and the electric potential on the surface was measured using a static electricity detector (model SV-511 of Static Co., Ltd.)

(1-4) Attachment of Shavings of Dry Bonito

After a multi-layer container was kept at 40° C. and 80% relative humidity for 24 hours, the surface was rubbed 10 times with cotton cloth, shavings of dried bonito were brought near the container and their attachment state was observed.

◯: not attached at all

Δ: attached to some extent

×: attached promptly

(2) Slip Performance

(2-1) Coefficient of Friction (Inclination Angle Method)

A sample film or a cardboard to be measured was put on a base plate surface. The same sample film was stuck on a lower part of load to be contacted with the base plate, and the base plate was inclined. The coefficient of friction was calculated from an angle at the time that the load started sliding.

(3) Scratch-proof Ability

(3-1) Reciprocating Sliding Abrasion

Using a sheet of cotton canvas No.10, under a condition of 430 g of load, 224 m² of contact area, 60 times/min of reciprocating speed and 100 times of reciprocating, the surface of a laminate was scratched and a ratio of shaved surface area was determined with a microscope photograph (35 times, observed 2 mm wide).

⊚: shaved part of less than 5%

◯: shaved part of 5% to less than 25%

Δ: shaved part of 25% to less than 50%

×: shaved part of 50% or more.

Example 1

Using multi-layer cast film machine, a multi-layer film having the first layer (the surface layer) made of MPE-2, the second layer (a middle layer) made of KIO-2 and the third layer (the surface layer) made of MPE-2, and having a thickness of each layer described in Table 4 was prepared. The thickness ratio of the first layer to the second layer of this multi-layer structure (Layer Thickness Ratio) was 0.75. The evaluation result of the first layer surface of multi-layer film obtained is shown in Table4.

Example 2

Using adhesive polyolefin Admer (trade name) NF528528 (MFR 2.2 g/10 min), produced by Mitsui chemicals Inc., as adhesive layers between the first layer made of MPE-2 and the second layer made of KIO-2, and between the second layer made of KIO-2 and the third layer made of MPE-2, a multi-layer film was prepared in the same manner as Example 1 except thickness ratio of each layer was changed as described in Table 4. The layer thickness ratio of a sum of the first layer thickness and the upper adhesive layer thickness to the second layer thickness, and the evaluation result of the antistatic performance of the first layer surface are shown in Table 4.

Example 3

A multi-layer film was prepared in the same manner as Example 2 except the first layer and the third layer were changed from MPE-2 to MPE-1 and thickness of each layer was changed as described in Table 4. The layer thickness ratio and the evaluation result of antistatic performance of the first layer surface are shown Table 4.

Examples 4 and 5

A multi-layer film was prepared in the same manner as Example 1 except use of HM-1 as the first layer, use of melt blend of EVA-1 and KIO-1 (weight ratio 80/20) as the second layer, use of EVA-2 as the third layer, and thickness of each layer was changed as described in Table 4. The layer thickness ratio and the evaluation result of the antistatic performance of the first layer surface are shown in Table 4.

Comparative Example 1

Using multi-layer cast film machine, a monolayer film of MPE-2 (50 μm thickness) was prepared by changing each layer to MPE-2. The antistatic performance of the surface of the monolayer film obtained was completely insufficient as shown in Table 4.

Comparative Example 2

A multi-layer film was prepared in the same manner as Example 3 except the second layer was changed from KIO-2 to HM-2. The antistatic performance of the first layer surface of the multi-layer film obtained was completely insufficient as shown in Table 4. TABLE 4 Examples Comp. Examples 1 2 3 4 5 1 2 Structure and 1st Layer MPE-2 MPE-2 MPE-1 HM-1 HM-1 MPE-2 MPE-1 Thickness of (15) (10) (20) (50) (200) (50) (20) Multi-layer Ad. Layer — NF528 NF528 — — — NF528 films (μm) (5) (20) (20) 2nd Layer KIO-2 KIO-2 KIO-2 EVA − 1 + EVA − 1 + — HM-2 (20) (20) (40) KIO − 1 KIO − 1 (40) Ad. Layer — NF528 NF528 — — — NF528 (5) (20) (20) 3rd Layer MPE-2 MPE-2 MPE-1 EVA-2 EVA-2 — MPE-1 (15) (10) (20) (40) (40) (20) Layer Thickness Ratio⁽¹⁾ 0.75 0.75 1.0 1.25 5.0 — 1.0 Evaluation of 1st Layer Surface 10% Charge Decay Time 0.01 10 0.79 0.02 0.02 60< 60< (sec) 50% Charge Decay Time — 0.01 0.04 0.01 — — — (sec) Cigarette Ash Test ⊚ ⊚ ◯ ⊚ ◯ X X (1) Layer Thickness Ratio: (1st layer + Upper Ad. Layer)/2nd Layer

Examples 6 to 10, Comparative Example 3

Using a blow-molding machine, a three-layer container was prepared with the layer structure shown in Table 5, 0.5 mm of thickness of each layer and 100 ml of inside volume. The evaluation result of outer layer surface of the container is shown together in Table 5. TABLE 5 Com. Examples Example 6 7 8 9 10 3 Layer Structure Outer Layer EVA-3 PE-1 EVA-3 PE-2 PE-2 PE-1 Middle Layer KIO-2 KIO-2 Blend* of KIO-2 Blend* of KIO-3 Blend* of KIO-4 (70) and PE-1(30) (70) and PE2(30) (20) and PE 2(80) PE-1 Inner Layer PE-1 PE-1 PE-1 PE-2 PE-2 PE-1 Evaluation of Outer Layer Surface Voltage(kV) 1 12 3 11 10 18 10% Charge Decay 0.03 15 0.27 11 3 No Time (sec) Decay 50% Charge Decay 0.01 0.15 0.04 0.12 0.07 Immeas- Time (sec) urable Dry Bonito ◯ Δ ◯ Δ ◯ X Shavings Test *Blend Ratio (by weight)

Example 11

Using a multi-layer cast film machine, a multi-layer film having the first layer (surface layer) made of KIO-2, the second layer (surface layer) made of MPE-1 and an adhesive layer made of adhesive polyolefin produced by Mitsui Chemicals Inc., Admer (trade name) NF528 (MFR 2.2 g/10 min) was prepared. Thickness structure of each layer is described in Table 6. The ratio of a sum of the second layer thickness and adhesive layer thickness to thickness of the first layer of this multi-layer structure (Layer Thickness Ratio) was 1.5. The evaluation results of the first layer surface and the second layer surface of the multi-layer film obtained are shown in Table 6.

Example 12

A multi-layer film was prepared in the same manner as Example 11 except KIO-2 of the first layer was changed to KIO-5. The layer thickness ratio of the multi-layer film obtained and the evaluation result of the antistatic performance of the first layer surface and the second layer surface of the film are shown in Table 6.

Example 13

A multi-layer film was prepared in the same manner as Example 11 except MPE-1 of second layer was changed to EVA-2 and thickness of each layer was changed as described in Table 6 without adhesive layer. The layer thickness ratio of the multi-layer film obtained and the evaluation result of the antistatic performance of the first layer surface and the second layer surface of the film are shown in Table 6.

Comparative Example 4

A multi-layer film was prepared in the same manner as Example 11 except KIO-2 of the first layer was changed to HM-2 and thickness of each layer was changed as described in Table 6. The antistatic performance of the surface of the first layer and the second layer of the multi-layer film obtained, and the coefficient of friction of the surface of the first layer were completely insufficient as shown in Table 6.

Comparative Example 5

A monolayer film (thickness 40 μm) of MPE-1 was prepared by changing each layer to MPE-1. The antistatic performance, coefficient of friction and abrasion resistance were completely insufficient as shown in Table 6. TABLE 6 Examples Comparative Examples 11 12 13 4 5 Constitution and 1st Layer KIO-2 (40) KIO-5 (40) KIO-2 (50) HM-2 (40) MPE-1 (40) Thickness of Multi- Ad. Layer NF528 (20) NF528 (20) — NF528 (20) — layer Films (μm) 2nd Layer MPE-1 (40) MPE-1 (40) EVA-2 (50) MPE-1 (40) — Layer Thickness Ratio⁽¹⁾ 1.5 1.5 1.0 1.0 — Evaluation of 1st Layer Surface 10% Charge Decay Time (sec) 0.01 0.01 0.01 — 60< 50% Charge Decay Time (sec) 0.01 — — 60< — Cigarette Ash Test ⊚ ⊚ ⊚ X X Coefficient of Among Films 0.53 0.60 0.53 2.4< 2.4< Sliding Friction To Cardboard 0.51 0.55 0.51 0.85 0.87 Reciprocating Sliding Abrasion Δ Δ Δ ⊚ X Evaluation of 2nd Layer Surface 10% Charge Decay Time (sec) 0.43 0.01 0.01 — 60< 50% Charge Decay Time (sec) 0.01 — — 60< — Cigarette Ash Test ⊚ ⊚ ⊚ X X (1) Layer Thickness Ratio; (2nd layer + Ad. Layer)/1st Layer

Example 14

A three-layer container with the layer structure shown in Table 7, 0.5 mm of thickness of each layer and 100 ml of inside volume was prepared using a blow-molding machine. The surface reflected gloss (in accordance with JIS Z8741) of this multi-layer container was 0.5%, the haze (in accordance with JIS K6714) was 65%, and the flexural modulus (in accordance with JIS K7106) was 147 MPa. The evaluation result of the antistatic performance is shown in Table 7.

Examples 15 to 17, Comparative Example 6

A three-layer container was prepared in the same manner as Example 14 except the layer structure was described in Table 7. The evaluation result of the antistatic performance is shown in Table 7. TABLE 7 Examples Com. Ex. 14 15 16 17 6 Layer Structure Outer Layer KIO-2 Blend* of KIO-3(80) PE-2 Blend* of KIO-4(20) PE-3 and PE-2(20) and PE-2(80) Middle Layer EVA-4 PE-2 PE-2 PE-2 PE-3 Inner Layer PE-3 PE-2 Blend of KIO-3(90) PE-2 PE-3 and PE-2(10) Evaluation of Outer Layer Surface Voltage (kV) 1 3 2 0 18 Dry Bonito ◯ ◯ ◯ ◯ X Shaving Test *Blend Ratio (by weight) Industrial Applicability

According to the present invention, a multi-layer structure which has good charge decay characteristics and dust-free characteristics to be able to prevent from adhesion of dust and powders due to static charge buildup can be provided. Moreover, a multi-layer structure having good slip characteristics and scratch resistance can be provided. Such structure is capable of serving various needs, for example, in the form of film, tape, sheet, tube, pipe, bag, multi-layer container (such as blow-molded container), rod, injection moldings, blow-molded articles, etc. This material is favorably employed especially for packaging materials. Such bags or multi-layer containers, in which the potassium ionomer layer (X) is the outer layer, exhibit good slip characteristics, scratch resistance and dust-free characteristics on their outer surface and at the same time can serve as good packaging materials having good heat sealability and antistatic properties on their inner surface. Above all, such multi-layer containers having the potassium ionomer layer (X) as the outer layer make bottles whose outer surface exhibits good slip characteristics, scratch resistance and dust-free characteristics and at the same time present a good appearance by virtue of low surface reflection gloss, high degree of haze, and silky appearance which contribute to the creation of high visual qualities in the resultant bottles. Bags or multi-layer containers which have the potassium ionomer layer (X) for their inner surface can be utilized as packaging materials whose inner surface possesses good ability to protect the packaged material from wear, slip characteristics and heat sealability, on top of the dust-free characteristics of their outer surface. Moreover such moldings having the potassium ionomer layer (X) for their intermediate layer and the surface layer (Y) possessing the aforesaid charge decay characteristics for their outer surface are found to have significant dust-free characteristics and be able to be avoid dust accumulation on the surface. And, where it is put in use as the material for packaging powders in such a manner that the surface layer (Y) having the aforesaid charge decay characteristics serves as the inner surface material, static adhesion of powder to the package does not take place, and hence the commercial value of such commodity is maintained. The outer surface of the multi-layer blow-molded containers constructed of the multi-layer structure of the present invention that incorporates the potassium ionomer layer for the intermediate layer exhibits good slip characteristics, scratch resistance and dust-free characteristics.

The multi-layer structure of the present invention can be utilized for the following applications in addition to the packaging material use. Namely, semiconductor-use adhesive tape or film such as dicing tape's substrate, back grinding film; materials utilized in the electric and electronic industries, such as marking film, IC carrier tape, electronic component taping; food wrapping material; sanitary supplies; surface protection film (i. e. guard film or tape for glass, plastic or metal board, and lens); steel wire sheathing or coating; clean room curtains, wall paper, mat, flooring, flexible container lining, container, shoes, battery separators, moisture permeable film, dust-free film, dust-proof film, substitute for PVC film; tubes and bottles to package cosmetics, detergents, shampoo, hair rinse, auto exterior or interior materials, etc.

The multi-layer structure of the present invention can be put into service after it has been provided with an adhesive layer on one side or the both sides of its surface layer. Examples of such adhesive layer are rubber-based, acrylic and silicone adhesive layers. The multi-layer structure of the present invention, moreover, can be utilized in the form of being laminated onto such substrate as biaxially oriented film or sheet produced from polyethyleneterephthalate, polyamide, and polypropylene, or items including sheet-form articles molded from acrylic resin, polycarbonate, ABS resin, styrene-based resin like polystyrene and polyacetal. In cases where the material is utilized as the surface material endowed with dust-free characteristic, the multi-layer structure of the present invention is laminated in a way that the layer (Y), the layer (X) or the layer (Z) contacts the aforesaid substrate face-to-face or laid over the substrate with an adhesive layer interposed in between. Examples of the substrate employed for the aforesaid applications can be monolayer or multi-layer materials produced from various plastics, paper, wood, metal foil and sheet, foams, woven fabric and nonwoven fabric. 

1. A multi-layer structure which comprises at least two layers including a layer (X) comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer or a mixture of said potassium ionomer and a thermoplastic polymer, and a layer (Y) comprising a polymer material having a surface resistivity of 1×10¹⁴ Ω or more, wherein at least one surface layer has a 10% charge decay, time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%.
 2. A multi-layer structure according to claim 1, wherein one of the surface layers consists of the layer (Y).
 3. A multi-layer structure according to claim 2, wherein one of the surface layers consists of the layer (X) and the other surface layer consists of the layer (Y), the layer (X) having a 10% charge decay time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50% and the layer Y having a 10% charge decay time of 20 sec or more at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%.
 4. A multi-layer structure which comprises at least two layers including a layer (X) comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer or a mixture of the potassium ionomer and a thermoplastic polymer, wherein a layer (Y), at least one of the surface layers, comprises a polymer material having a surface resistivity of 1×10¹⁴ Ω or more and the surface layer (Y) has a 10% charge decay time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%.
 5. A multi-layer structure according to claim 4, wherein the other surface layer consists of the layer (X).
 6. A multi-layer structure according to claim 5, wherein the other surface layer (X) has a 10% charge decay time of 20 sec or less at +5000V applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%.
 7. A multi-layer structure according to claim 4, wherein the structure is constructed of three or more layers and is characterized that the layer (X) is the intermediate layer and the other surface layer (Z) comprises a polymer material having a surface resistivity of 1×10¹⁴ Ω or more.
 8. A multi-layer structure according to claim 7, wherein the surface layer (Z) has a 10% charge decay time of 20 sec or less at +5000 v applied voltage as determined in atmosphere at a temperature of 23° C. and a relative humidity of 50%.
 9. A multi-layer structure according to claim 1 or 4 wherein the potassium ionomer comprises an ionomer of the ethylene-unsaturated carboxylic acid copolymer whose unsaturated carboxylic acid content is 10 to 30% by weight, having a neutralization degree of 60% or more by potassium ion.
 10. A multi-layer structure according to claim 9, wherein the potassium ionomer is mixed ionomers of two or more ethylene-unsaturated carboxylic acid polymers varying in the unsaturated carboxylic acid content, the average acid content of the ethylene-unsaturated carboxylic acid copolymers being 10 to 20% by weight and the difference in the acid content between the highest and the lowest acid contents being 2 to 20% by weight.
 11. A multi-layer structure according to claim 10, wherein the potassium ionomer is mixed ionomers of mixed copolymer composition, having an average unsaturated carboxylic acid content of 10 to 30% by weight and average melt flow rate of 1 to 300 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g, and has a degree of neutralization of 60% or more, which comprises an ethylene-unsaturated carboxylic acid copolymer (copolymer (A-1)) having an unsaturated carboxylic acid content of 1 to 10% by weight and a melt flow rate of 1 to 600 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g and an ethylene-unsaturated carboxylic acid copolymer (copolymer (A-2)) having an unsaturated carboxylic acid content of 11 to 25% by weight and a melt flow rate of 1 to 600 g/10 min as determined at a temperature of 190° C. and under a load of 2,160 g.
 12. A multi-layer structure according to claim 11, wherein the mixed copolymer composition is prepared in the blending ratio of 5 to 80% by weight for the ethylene-unsaturated carboxylic acid copolymer (copolymer (A-1)) and 95 to 20% by weight for the ethylene-unsaturated carboxylic acid copolymer (copolymer (A-2)).
 13. A multi-layer structure according to claim 9, wherein a polyhydroxy compound is blended in the layer (X) in the ratio of 15% by weight or less against the amount of the potassium ionomer.
 14. A multi-layer structure according to claim 9, wherein a polyhydroxy compound is blended in the layer (X) in the ratio of less than 0.1% against the amount of the potassium ionomer.
 15. A multi-layer structure according to claim 1 or 4, wherein the thermoplastic polymer in the layer (X) is an olefin-based polymer.
 16. A multi-layer structure according to claim 1 or 4, wherein the polymer material of the layer (Y) is an olefin-based polymer.
 17. A multi-layer structure according to claim 16, wherein the olefin-based polymer is linear low density polyethylene or zinc ionomer.
 18. A multi-layer structure according to claim 17, wherein the linear low density polyethylene is an ethylene polymer or copolymer produced by metallocene catalyst.
 19. A multi-layer structure according to claim 7, wherein the polymer material of the layer (Z) is an olefin-based polymer.
 20. A multi-layer structure according to claim 19, wherein the olefin-based polymer is linear low density polyethylene or zinc ionomer.
 21. A multi-layer structure according to claim 20, wherein the linear low density polyethylene is an ethylene copolymer produced by metallocene catalyst.
 22. A multi-layer structure according to claim 4, wherein the structure is constructed of the following three layers: (a) a layer comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer, (b) a layer comprising linear low density polyethylene or a mixture of 100 parts by weight of linear low density polyethylene and 100 parts or less by weight of a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer, and (c) a layer comprising linear low density polyethylene.
 23. A multi-layer structure according to claim 7, wherein the structure is constructed of the following three layers: (a) a layer comprising polyethylene or ethylene-unsaturated ester copolymer, (b) a layer comprising a potassium ionomer of ethylene-unsaturated carboxylic acid copolymer or a mixture of the potassium ionomer and thermoplastic polymer, and (C) a layer comprising polyethylene or ethylene-unsaturated ester copolymer.
 24. A multi-layer structure according to claim 4, wherein an adhesive layer and/or recycled resin layer is incorporated in between the layer (X) and the layer (Y).
 25. A multi-layer structure according to claim 3, which is constructed of the following three layers: (a) a layer comprising foamed or non-foamed potassium ionomer of ethylene-unsaturated carboxylic acid copolymer, (b) a layer comprising an ethylene-unsaturated ester copolymer, and (C) a layer comprising polyethylene.
 26. A multi-layer structure according to claim 7, wherein an adhesive layer and/or recycled resin layer is incorporated in between the layer (X) and the layer (Z).
 27. A multi-layer structure according to claim 1 or 4, wherein the thickness ratio of the total thickness of other layers to the layer (X) is within a range of 0.1 to
 100. 28. A sheet or film which comprises the multi-layer structure according to claim 1 or
 4. 29. A sheet or film according to claim 28 whose coefficient of friction is 1.0 or less.
 30. A sheet or film according to claim 28 which is applied for packaging use.
 31. A bag or multi-layer container which is constructed of the multi-layer structure according claim 1 or
 4. 32. A multi-layer container according to claim 31, wherein the container is produced by the blow molding process.
 33. A bag or a multi-layer container according to claim 31, wherein the layer (X) is used as the innermost or outermost layer.
 34. Flooring which is constructed of the multi-layer =structure according to claim 1 or
 4. 